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Journal of the American Pomological Society
(J Am Pom Soc)

American Pomological Society

Volume 73 Number 4 Article 5 Pages: 240-253
Year 2019 Month 10
Title: Noninfectious Bud-failure As a Model For Studying Age Related Genetic Disorders in Long-Lived Perennial Plants
Authors: Thomas Gradziel, and Jonathan Fresnedo
Plants disseminated through vegetative propagation avoid the meiotic recombination and associated rejuvenation found during sexual seed propagation. The resulting natural and human selected clones allow accumulation of genetic as well as non-genetic (epigenetic) interactions as long as the studied trait remain trueto- type following vegetative propagation. The consequent ‘immortalization’ of the clone also allows large clonal population sizes and long-term plant lifespans required for the later accumulation of budsport mutations in such long-lived genotypes. While both natural and human selection result in clones with desirable changes, the longterm preservation of these clones also facilitate the occurance of genetic disorders. In almond (Prunus dulcis, DA Webb) Noninfectious Bud-failure (NBF) is an economically important disorder of California cultivars because it severely affects two major commercial cultivars, ‘Nonpareil’ and ‘Carmel’, and has led to the abandonment of many otherwise productive cultivars and breeding selections over the last half century. NBF expression shows some epigenetic characteristics including an increase in expression with tree as well as clone age, so that new cultivars may possess the NBF factor but it remains latent for years to decades. The resulting tree and clone aging ‘time-bomb’ makes this disorder particularly devastating since extensive commercial plantings may have been established before the disorder is first identified. Because of this economic significance, clone lineage or clone-source selection strategies have been developed to identify this disorder within breeding lineages as well as within individual nursery propagation sources. Proven though somewhat tedious phenotype-based methods for identifying NBF-associated factors, both among and within genotypes have proven effective in 30 years of field testing. Results from preliminary characterizations of DNA-(de)methylation profiling using methylationsensitive amplified fragment length polymorphisms (MS-AFLP) targeting NBF and the related aging-process within individual plants as well as within individual clones has provided promising insights. Challenges remain in identifying both the mechanism as well as governing tissue for clonal age-memory in plants.

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